We have performed magneto-transport measurements on a two-dimensional electron system (2DES) in the vicinity of nanoscaled scatterers. Weak localization as evidenced by negative magnetoresistance is observed and we use the extracted phase coherence rate as a thermometer to measure the effective electron temperature Te in our 2DES when a high current I flows in the device. It is found that TeαI~0.5, consistent with 1/τep~T2 in two dimensions, where 1/τep is the electron-phonon scattering. However, it is worth mentioning that the phase coherence rate 1/τΦ~ T, in agreement with the fact that at low temperatures the dominant phase-breaking mechanism is electron-electron scattering, not electron-phonon scattering. Therefore we are able to investigate the two different inelastic scattering mechanisms which are, in most cases, difficult to be studied independently. Moreover, our data shows that the electron heating effect is a powerful tool to study nanostructures.